Minies probably will not work as the rifling will be too deep on an inline and you end up loosing accuracy due to gas leakage. Better bet would be to find sabots and shoot pistol bullets out of it. Your twist rate is fast on an in line, usually in the 1 in 24 twist so going with a conical bullet will probably not give you good results. The sabot combo would need a .452 sized bullet in .50 cal but the sabot will be .50 and acts as a gas check and imparts the spin to the bullet. In lines as far as bullets go are a totally different animal than say a hawken with a 1 in 48 twist or a rifle musket with a 1 in 66 or 1 in 72 twist.
mack
hitler, stalin and mao were progressives in their time